While substantial effort and attention continues toward the development of newer and more sustainable energy supplies, the conservation of energy by increased energy efficiency remains crucial to the world's energy future. According to an October 2010 report from the U.S. Department of Energy, heating and cooling account for 56% of the energy use in a typical U.S. home, making it the largest energy expense for most homes. Along with improvements in the physical plant associated with home heating and cooling (e.g., improved insulation, higher efficiency furnaces), substantial increases in energy efficiency can be achieved by better control and regulation of home heating and cooling equipment. By activating heating, ventilation, and air conditioning (HVAC) equipment for judiciously selected time intervals and carefully chosen operating levels, substantial energy can be saved while at the same time keeping the living space suitably comfortable for its occupants.
Historically, however, most known HVAC thermostatic control systems have tended to fall into one of two opposing categories, neither of which is believed be optimal in most practical home environments. In a first category are many simple, non-programmable home thermostats, each typically consisting of a single mechanical or electrical dial for setting a desired temperature and a single HEAT-FAN-OFF-AC switch. While being easy to whether the thermostat is installed use for even the most unsophisticated occupant, any energy-saving control activity, such as adjusting the nighttime temperature or turning off all heating/cooling just before departing the home, must be performed manually by the user. As such, substantial energy-saving opportunities are often missed for all but the most vigilant users. Moreover, more advanced energy-saving settings are not provided, such as the ability to specify a custom temperature swing, i.e., the difference between the desired set temperature and actual current temperature (such as 1 to 3 degrees) required to trigger turn-on of the heating/cooling unit.
In a second category, on the other hand, are many programmable thermostats, which have become more prevalent in recent years in view of Energy Star (US) and TCO (Europe) standards, and which have progressed considerably in the number of different settings for an HVAC system that can be individually manipulated. Unfortunately, however, users are often intimidated by a dizzying array of switches and controls laid out in various configurations on the face of the thermostat or behind a panel door on the thermostat, and seldom adjust the manufacturer defaults to optimize their own energy usage. Thus, even though the installed programmable thermostats in a large number of homes are technologically capable of operating the HVAC equipment with energy-saving profiles, it is often the case that only the one-size-fits-all manufacturer default profiles are ever implemented in a large number of homes. Indeed, in an unfortunately large number of cases, a home user may permanently operate the unit in a “temporary” or “hold” mode, manually manipulating the displayed set temperature as if the unit were a simple, non-programmable thermostat.
At a more general level, because of the fact that human beings must inevitably be involved, there is a tension that arises between (i) the amount of energy-saving sophistication that can be offered by an HVAC control system, and (ii) the extent to which that energy-saving sophistication can be put to practical, everyday use in a large number of homes. Similar issues arise in the context of multi-unit apartment buildings, hotels, retail stores, office buildings, industrial buildings, and more generally any living space or work space having one or more HVAC systems. Other issues arise as would be apparent to one skilled in the art upon reading the present disclosure.
It is to be appreciated that although exemplary embodiments are presented herein for the particular context of HVAC system control, there are a wide variety of other resource usage contexts for which the embodiments are readily applicable including, but not limited to, water usage, air usage, the usage of other natural resources, and the usage of other (i.e., non-HVAC-related) forms of energy, as would be apparent to the skilled artisan in view of the present disclosure. Therefore, such application of the embodiments in such other resource usage contexts is not outside the scope of the present teachings.
In some embodiments, a thermostat for controlling an HVAC system in an enclosure may include a passive infrared sensor, an active infrared sensor, an electronic display having a first mode and a second mode, and one or more processors coupled to the passive infrared sensor, the active infrared sensor, and the electronic display. The one or more processors may be programmed to change a setpoint temperature of the thermostat to an energy-saving temperature upon detection of a non-occupancy condition for the enclosure, where the one or more processors may detect the non-occupancy condition based at least in part on readings received from the passive infrared sensor. The one or more processors may also be programmed to change the electronic display from the first mode to the second mode upon detection of a person approaching the thermostat. The one or more processors may detect a person approaching the thermostat based at least in part on readings received from the active infrared sensor.
In some embodiments, a method for controlling an HVAC system in an enclosure using a thermostat may include operating a passive infrared sensor of the thermostat, operating an active infrared sensor of the thermostat, and operating an electronic display of the thermostat in a first mode. The method may also include receiving, by one or more processors of the thermostat, readings from the passive infrared sensor and readings from the active infrared sensor. The method may additionally include detecting, by the one or more processors, a non-occupancy condition for the enclosure based at least in part on readings received from the passive infrared sensor. The method may further include changing, by the one or more processors, a setpoint temperature of the thermostat to an energy-saving temperature upon detection of the non-occupancy condition for the enclosure. The method may also include detecting, by the one or more processors, a person approaching the thermostat based at least in part on readings received from the active infrared sensor. The method may additionally include changing, by the one or more processors, the electronic display from the first mode to a second mode upon detection of the person approaching the thermostat.
In some embodiments, a non-transitory storage medium may include instructions that, when executed by one or more processors, cause the one or more processors to perform operations including receiving readings from a passive infrared sensor and detecting a non-occupancy condition for an enclosure based at least in part on the readings received from the passive infrared sensor. The operations may also include changing a setpoint temperature of a thermostat to an energy-saving temperature upon detection of the non-occupancy condition for the enclosure. The operations may additionally include receiving readings from an active infrared sensor. The operations may further include detecting, by the one or more processors, a person approaching the thermostat based at least in part on readings received from the active infrared sensor. The operations may also include changing, by the one or more processors, an electronic display of the thermostat from a first mode to a second mode upon detection of the person approaching the thermostat.
Various implementations of these embodiments may include one or more of the following features in any combination and without restriction. The passive infrared sensor and the active infrared sensor may be positioned behind a darkened front cover of the thermostat such that the darkened front cover of the thermostat conceals the passive infrared sensor and the active infrared sensor from the view of a user. The detection of the non-occupancy condition for the enclosure may include detecting a time interval of between 30 minutes and 150 minutes in which no readings indicative of a user presence are received by the passive infrared sensor. The first mode of the electronic display may cause the thermostat to use a first amount of power, and the second mode of the electronic display may cause the thermostat to use a second amount of power. The first mode of the electronic display may indicate a non-readiness to interact with a user, and the second mode of the electronic display may indicate a readiness to interact with the user. The active infrared sensor and/or the one or more processors may be configured to detect a person approaching the thermostat within a predetermined distance that indicates an intent of a user to walk up to the thermostat. The electronic display may include a touch-sensitive display with sliding touch controls. The thermostat may also include a Wi-Fi module that is programmed to receive a command from a mobile computing device. The thermostat may enter an energy-saving mode in response to receiving the command from the mobile computer device, and an indication that the thermostat is in the energy-saving mode may be displayed on the electronic display when the electronic display is in the second mode.